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1.
Biswanath Das Chithaluri Sudhakar Parigi Raghavendar Reddy Jajula Kashanna 《Helvetica chimica acta》2011,94(6):1048-1052
Treatment of {[(benzyloxy)carbonyl]amino}‐substituted sulfones 1 with 2‐[(trimethylsilyl)oxy]furan ( 2 ) in the presence of InCl3 as a catalyst at room temperature produced the γ‐butenolactone derivatives 3 and 4 containing a protected amino group (Scheme 1). The products were formed in high yields (81–92%) within 3–10 h favoring the anti‐isomer 3 . 相似文献
2.
The photochemical behavior of various substituted epoxycarbonyl compounds consisting of more than one possible photo‐labile site (i.e. δ‐hydrogen, β‐hydrogen and epoxide ring) has been investigated. These compounds on photo‐irradiation produced the β‐hydroxyenones in an eco‐friendly green approach. Mechanistically, these photo‐transformations have been envisaged to occur via an intramolecular β‐hydrogen abstraction by the carbonyl group of benzoyl moiety to generate the 1,3‐biradical followed by epoxide ring opening that isomerizes into the photoproducts. The photolysis of the probed epoxy ketones didn’t furnish any photoproduct through δ‐hydrogen abstraction, whatsoever. This exclusive preference for β‐H abstraction over δ‐H abstraction by carbonyl group has been vindicated by the MM2 energy mini‐ mized program for the investigated photochemical substrates. The structures of these photoproducts were established from the analysis of their spectral parameters (IR, 1H/13C NMR and Mass) and single crystal X‐ray crystallography data. 相似文献
3.
Dieter Seebach 《Helvetica chimica acta》2011,94(1):1-17
Fmoc‐β2hSer(tBu)‐OH was converted to Fmoc‐β2hSec(PMB)‐OH in five steps. To avoid elimination of HSeR, the selenyl group was introduced in the second last step (Fmoc‐β2hSer(Ts)‐OAll→Fmoc‐β2hSec(PMB)‐OAll). In a similar way, the N‐Boc‐protected compound was prepared. With the β2hSe‐derivatives, 21 β2‐amino‐acid building blocks with proteinogenic side chains are now available for peptide synthesis. 相似文献
4.
Luis G. Hernández‐Vázquez Marco A. Leyva Alejandro J. Metta‐Magaña Jaime Escalante 《Helvetica chimica acta》2012,95(11):2218-2230
Different cyclo‐β‐dipeptides were prepared from corresponding N‐substituted β‐alanine derivatives under mild conditions using PhPOCl2 as activating agent in benzene and Et3N as base. To evaluate β3‐substituent influence, the amino acids 7 – 26 were synthesized, and a β‐lactam formation reaction was carried out instead of cyclo‐β‐dipeptide formation. The crystal structures of three derivatives of cyclo‐β‐peptides and one β‐lactam are presented. 相似文献
5.
Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds
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Abdolali Alizadeh Seyed Yasub Hosseini Hadi Sedighian Fahimeh Bayat 《Helvetica chimica acta》2015,98(10):1426-1434
Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, 1H‐ and 13C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1). 相似文献
6.
Christian Chapuis Michel Barthe Carole Cantatore Christine Saint‐Lger Patrick Wyss 《Helvetica chimica acta》2006,89(11):2638-2653
To complete our panorama in structure–activity relationships (SARs) of sandalwood‐like alcohols derived from analogues of α‐campholenal (= (1R)‐2,2,3‐trimethylcyclopent‐3‐ene‐1‐acetaldehyde), we isomerized the epoxy‐isopropyl‐apopinene (?)‐ 2d to the corresponding unreported α‐campholenal analogue (+)‐ 4d (Scheme 1). Derived from the known 3‐demethyl‐α‐campholenal (+)‐ 4a , we prepared the saturated analogue (+)‐ 5a by hydrogenation, while the heterocyclic aldehyde (+)‐ 5b was obtained via a Bayer‐Villiger reaction from the known methyl ketone (+)‐ 6 . Oxidative hydroboration of the known α‐campholenal acetal (?)‐ 8b allowed, after subsequent oxidation of alcohol (+)‐ 9b to ketone (+)‐ 10 , and appropriate alkyl Grignard reaction, access to the 3,4‐disubstituted analogues (+)‐ 4f,g following dehydration and deprotection. (Scheme 2). Epoxidation of either (+)‐ 4b or its methyl ketone (+)‐ 4h , afforded stereoselectively the trans‐epoxy derivatives 11a,b , while the minor cis‐stereoisomer (+)‐ 12a was isolated by chromatography (trans/cis of the epoxy moiety relative to the C2 or C3 side chain). Alternatively, the corresponding trans‐epoxy alcohol or acetate 13a,b was obtained either by reduction/esterification from trans‐epoxy aldehyde (+)‐ 11a or by stereoselective epoxidation of the α‐campholenol (+)‐ 15a or of its acetate (?)‐ 15b , respectively. Their cis‐analogues were prepared starting from (+)‐ 12a . Either (+)‐ 4h or (?)‐ 11b , was submitted to a Bayer‐Villiger oxidation to afford acetate (?)‐ 16a . Since isomerizations of (?)‐ 16 lead preferentially to β‐campholene isomers, we followed a known procedure for the isomerization of (?)‐epoxyverbenone (?)‐ 2e to the norcampholenal analogue (+)‐ 19a . Reduction and subsequent protection afforded the silyl ether (?)‐ 19c , which was stereoselectively hydroborated under oxidative condition to afford the secondary alcohol (+)‐ 20c . Further oxidation and epimerization furnished the trans‐ketone (?)‐ 17a , a known intermediate of either (+)‐β‐necrodol (= (+)‐(1S,3S)‐2,2,3‐trimethyl‐4‐methylenecyclopentanemethanol; 17c ) or (+)‐(Z)‐lancifolol (= (1S,3R,4Z)‐2,2,3‐trimethyl‐4‐(4‐methylpent‐3‐enylidene)cyclopentanemethanol). Finally, hydrogenation of (+)‐ 4b gave the saturated cis‐aldehyde (+)‐ 21 , readily reduced to its corresponding alcohol (+)‐ 22a . Similarly, hydrogenation of β‐campholenol (= 2,3,3‐trimethylcyclopent‐1‐ene‐1‐ethanol) gave access via the cis‐alcohol rac‐ 23a , to the cis‐aldehyde rac‐ 24 . 相似文献
7.
Laurent Dufossé Dominique Cartier Benoist Valla Mireille Fouillaud Roger Labia Alain Valla 《Helvetica chimica acta》2013,96(2):259-265
Catalytic base‐induced decarboxylation of polyunsaturated α‐cyano‐β‐methyl acids derived from malonic acid led to the corresponding nitriles 3 (Schemes 2 and 3), 6 (Scheme 5), and 9 (Scheme 6). This decarboxylation occurred with previous deconjugation of the α,β‐alkene moiety of the α‐cyano‐β‐methyl acid, leading to an α‐cyano‐β‐methylene propanoic acid which was easily decarboxylated (see Scheme 2). β‐Methylene intermediates, in some cases, could be isolated; mechanistic pathways are proposed. The nitriles 3, 6 , and 9 were reduced to the sesquiterpene aldehydes 4 (β‐end group), 7 (φ‐end group), and 10 (ψ‐end group), respectively. 相似文献
8.
Stig Valdersnes Ingrid Apeland Guri Flemmen Leiv K. Sydnes 《Helvetica chimica acta》2012,95(11):2099-2122
Selected 5‐substituted derivatives 4 of 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one were treated with propane‐1,3‐dithiol under various conditions. The unprotected hydroxy ketones underwent cyclization during the dithiol addition and gave the corresponding 3‐(diethoxymethyl)‐2‐oxa‐6,10‐dithiaspiro[4.5]decan‐3‐ols 5 in 80–90% yield as the only products (Scheme 3 and Table 1). These products can be regarded as partly modified carbohydrates in the furanose form. When the benzyl‐protected analogues 10‐Bn of the 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one derivatives were treated with the same dithiol, however, no cyclization occurred; instead the corresponding 3‐{2‐[(benzyloxy)methyl]‐1,3‐dithian‐2‐yl}‐1,1‐diethoxypropan‐2‐one derivatives 11‐Bn were formed in good yield (up to 99%; Table 4). These 1,3‐dithianes were and are in the process of being converted to a number of new carbohydrate analogues, and here are reported high‐yield syntheses of functionalized molecules 17 belonging to the 5,5‐diethoxy‐1,4‐dihydroxypentan‐2‐one family of compounds (Table 7), via 15‐Bn (Table 5) and 16‐Bn (Table 6 and Scheme 8). 相似文献
9.
Iron carbonyl‐mediated alkene hydroamidation of 7‐oxabenzonorbornadiene was accomplished under very mild conditions as the result of nucleophilic attack of amines on iron‐coordinating CO to produce exo‐5‐(alkylaminocarbonyl)‐7‐oxabenzobicyclo[2.2.1]hept‐2‐ene derivatives. 相似文献
10.
Yang Jiang Bo Tan Zhong‐Zhou Chen Tong Liu Ru‐Gang Zhong Yan‐Mei Li David Jeremy Stewart Yu‐Fen Zhao Hua‐Liang Jiang 《International journal of quantum chemistry》2003,94(4):232-241
In recent years β‐amino acids have increased their importance enormously in defining secondary structures of β‐peptides. Interest in β‐amino acids raises the question: Why and how did nature choose α‐amino acids for the central role in life? In this article we present experimental results of MS and 31P NMR methods on the chemical behavior of N‐phosphorylated α‐alanine, β‐alanine, and γ‐amino butyric acid in different solvents. N‐Phosphoryl α‐alanine can self‐assemble to N‐phosphopeptides either in water or in organic solvents, while no assembly was observed for β‐ or γ‐amino acids. An intramolecular carboxylic–phosphoric mixed anhydride (IMCPA) is the key structure responsible for their chemical behaviors. Relative energies and solvent effects of three isomers of IMCPA derived from α‐alanine (2a–c), with five‐membered ring, and five isomers of IMCPA derived from β‐alanine (4a–e), with six‐membered ring, were calculated with density functional theory at the B3LYP/6‐31G** level. The lower relative energy (3.2 kcal/mol in water) of 2b and lower energy barrier for its formation (16.7 kcal/mol in water) are responsible for the peptide formation from N‐phosphoryl α‐alanine. Both experimental and theoretical studies indicate that the structural difference among α‐, β‐, and γ‐amino acids can be recognized by formation of IMCPA after N‐phosphorylation. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 232–241, 2003 相似文献
11.
Carbon, silicon, germanium, tin and lead‐centered radicals were reacted with 3‐nitropentan‐2‐one and 3‐nitropentan‐2‐ol inside the cavity of an electron paramagnetic resonance spectrometer. In all cases, selective addition to the nitrogroup was observed with detection of the corresponding oxynitroxide radicals. In the case of the carbonyl substrate, alkyl acyl nitroxides were also detected because of α‐photocleavage. The oxynitroxides decayed with a first order kinetics via fragmentation of the carbon–nitrogen bond (denitration). Unexpectedly, the activation parameters were fairly similar to those previously reported for the corresponding tert‐butyl oxynitroxides and almost independent from the presence of a carbonyl or a hydroxyl group on the carbon adjacent to the one bearing the nitrogroup. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
12.
Stereoselective Organocatalyzed Synthesis of α‐Fluorinated β‐Amino Thioesters and Their Application in Peptide Synthesis
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Dr. Jakub Saadi Dr. Marc‐Olivier Ebert Prof. Dr. Helma Wennemers 《Angewandte Chemie (International ed. in English)》2016,55(42):13127-13131
α‐Fluorinated β‐amino thioesters were obtained in high yields and stereoselectivities by organocatalyzed addition reactions of α‐fluorinated monothiomalonates (F‐MTMs) to N‐Cbz‐ and N‐Boc‐protected imines. The transformation requires catalyst loadings of only 1 mol % and proceeds under mild reaction conditions. The obtained addition products were readily used for coupling‐reagent‐free peptide synthesis in solution and on solid phase. The α‐fluoro‐β‐(carb)amido moiety showed distinct conformational preferences, as determined by crystal structure and NMR spectroscopic analysis. 相似文献
13.
A series of N‐aryl 2‐alkenamides were produced efficiently by treating N‐aryl 3‐(phenylsulfonyl)‐propanamides with potassium tert‐butoxide in THF at 0°C. With out isolation, it was further treated with an additional equivalent of potassium tert‐butoxide and allyl bromide to give N‐allyl N‐aryl 2‐alkenamides in one pot in good yields. Followed by a ring‐closing metathesis reaction, these N‐allyl N‐aryl 2‐alkenamides were respectively converted into corresponding N‐aryl α,β‐unsaturated γ‐lactams in moderate yields. 相似文献
14.
Johannes Schranck Mia Burhardt Christoph Bornschein Dr. Helfried Neumann Prof. Dr. Troels Skrydstrup Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9534-9538
A carbonylative α‐arylation process employing unactivated nitriles for the first time is described. The reaction tolerates a range of (hetero)aryl iodides and several nitrile coupling partners. No prefunctionalization of the nitriles is necessary and the resulting β‐ketonitriles are obtained in good to excellent yields. The methodology also allows for a convenient 13C‐labelling of the generated carbonyl moiety. 相似文献
15.
The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M+‐29], [M+‐55], and [M+‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed. 相似文献
16.
Jincui Ye Wenying Yu Guosheng Chen Zhengrong Shen Su Zeng 《Biomedical chromatography : BMC》2010,24(8):799-807
The enantio‐separations of eight 2‐arylpropionic acid nonsteroidal anti‐inflammatory drugs (2‐APA NSAIDs) were established using reversed‐phase high‐performance liquid chromatography with hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as chiral mobile phase additive for studying the stereoselective skin permeation of suprofen, ketoprofen, naproxen, indoprofen, fenoprofen, furbiprofen, ibuprofen and carprofen. The effects of the mobile phase composition, concentration of HP‐β‐CD and column temperature on retention and enantioselective separation were investigated. With 2‐APA NSAIDs as acidic analytes, the retention times and resolutions of the enantiomers were strongly related to the pH of the mobile phase. In addition, both the concentration of HP‐β‐CD and temperature had a great effect on retention time, but only a slight or almost no effect on resolutions of the analytes. Enantioseparations were achieved on a Shimpack CLC‐ODS (150 × 4.6 mm i.d., 5 μm) column. The mobile phase was a mixture of methanol and phosphate buffer (pH 4.0–5.5, 20 mM) containing 25 mM HP‐β‐CD. This method was flexible, simple and economically advantageous over the use of chiral stationary phase, and was successfully applied to the enantioselective determination of the racemic 2‐APA NSAIDs in an enantioselective skin permeation study. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
17.
Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters
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Rima Belibel Christel Barbaud 《Journal of polymer science. Part A, Polymer chemistry》2015,53(22):2586-2597
Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by 1H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597 相似文献
18.
β‐Bromo‐α,β‐unsaturated ketones are condensed with arylhydrazines to form hydrazones, which are in situ intramolecularly cyclized into 3‐substituted 1‐aryl‐1 H‐pyrazoles under a catalytic system of Pd(OAc)2/1,3‐bis(diphenylhosphino)propane (dppp)/NaOtBu. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
Antal Pter Gabriella Trk Gza Tth Wolfgang Lindner 《Journal of separation science》2000,23(11):628-636
A quinine‐derived chiral anion‐exchange stationary phase was used for the direct high‐performance liquid chromatographic separation of the enantiomers of the N‐protected unusual β‐substituted α‐amino acids, β‐methylphenylalanine, β‐methyltyrosine, β‐methyltryptophan, and β‐methyl‐1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid. The readily prepared 2,4‐dinitrophenyl and tert‐butyloxycarbonyl derivatives were well separated, and in most cases the separation of all four stereoisomers of these β‐methyl‐α‐amino acids could be obtained in one chromatographic run. The elution sequences of the enantiomers of the different derivatives were determined and revealed a dependence on the type of the N‐protecting group. In this context, the effects of different protecting groups (acetyl, tert‐butyloxycarbonyl, benzoyl, 3,5‐dinitrobenzoyl, benzyloxycarbonyl, 3,5‐dinitrobenzyloxycarbonyl, 2,4‐dinitrophenyl, and 9‐fluorenylmethoxycarbonyl) on the chromatographic behavior were investigated. 相似文献
20.
A Ph3P‐catalyzed cyclization of α‐halogeno ketones 2 with dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates) 3 produced halogenated α,β‐unsaturated γ‐butyrolactone derivatives 4 in good yields (Scheme 1, Table). The presence of electron‐withdrawing groups such as halogen atoms at the α‐position of the ketones was necessary in this reaction. Cyclization of α‐chloro ketones resulted in higher yields than that of the corresponding α‐bromo ketones. Dihalogeno ketones similarly afforded the expected γ‐butyrolactone derivatives in high yields. 相似文献